1. Field of the Invention
The present invention relates to a fluid dynamic pressure bearing using lubricating fluid, and a motor and a disk driving apparatus equipped with this fluid dynamic pressure bearing.
2. Description of the Related Art
A fluid dynamic pressure bearing using fluid pressure of lubricating oil filled between a shaft member and a sleeve member has been used so far to support both the shaft member and the sleeve member relatively rotatable to each other. This type of fluid dynamic pressure bearing is provided with thrust fluid dynamic pressure bearing means to support thrust load and radial fluid dynamic pressure bearing means to support radial load between the shaft member and the sleeve member. When such a fluid dynamic pressure bearing is used in a motor, either the shaft member or the sleeve member is fixed. That is, if the shaft member is fixed, a motor becomes of stationary shaft type and if the sleeve member is fixed, a motor becomes of rotary shaft type.
However, this type of fluid dynamic pressure bearing has such problems which are to be solved. That is, a conventional fluid dynamic pressure bearing so far in use is able to retain only minimum required lubricating oil and lubricating oil may decrease due to leakage, evaporation, etc. as a result of use, and the life of bearing may be expired in a relatively short period. Further, as there is no sufficient space for reserving lubricating oil, it was necessitated to accurately measure oil quantity to be filled in thrust fluid dynamic pressure bearing means and/or radial dynamic pressure bearing means and therefore, the conventional fluid dynamic pressure bearing was a bearing having an extremely less allowable margin when temperature fluctuation and secular change were taken into consideration.